This application claims the priority of Korean Patent Application No. 2003-29296, filed on May 9, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a phantom that can be tomographed by various medical imaging apparatuses after being built in each of the medical imaging apparatuses, and more particularly, to a phantom for evaluating accuracy of image registration software by matching and comparing images, taken by various medical imaging apparatuses, with one another with the use of imaging registration software.
2. Description of the Related Art
Recent developments in medical science and technology have enabled many medical procedures and diagnoses that at one time were considered impossible. One of these developments is imaging apparatuses, such as a computed tomography (CT) apparatus, a magnetic resonance imaging (MRI) apparatus, a single photon emission computed tomography (SPECT) apparatus, and a positron emission tomography (PET) apparatus, which enable a detailed observation of the entire human body, and thus is very important for diagnosing or treating diseases such as tumors or cancer.
Since the CT, MRI, SPECT, and PET apparatuses are based on different imaging principles and have different advantages and disadvantages, it is preferable to use the one that best fits the purpose of diagnosis.
The CT apparatus is an imaging apparatus that uses differences in X-ray attenuation coefficients among parts of, for example, the entire human body, which are caused by electron density variations. The CT apparatus can provide detailed anatomical images with fewer distortions. In particular, the CT apparatus provides excellent imaging of a bone structure of the entire human body. In addition, the CT apparatus allows electron density information to be immediately applied to dose calculations, and thus can provide standard images for the planning of radioactive treatments.
The MRI apparatus is an imaging apparatus that uses frequency conversion signals generated in the process of magnetizing and demagnetizing hydrogen atoms in the entire human body. The MRI apparatus provides anatomical images with high contrast and high resolution. However, there is a possibility of the MRI apparatus providing distorted images, which is mainly due to the irregularity of magnetic fields.
The SPECT apparatus is an imaging apparatus that forms images of parts of the entire human body by injecting a reagent containing radionuclides that emit gamma rays into a desired part of the entire human body and detecting the gamma rays emitted from the radionuclides. The SPECT apparatus is generally used for analyzing metabolism and nervous functions of the desired part of the entire human body. However, the SPECT apparatus provides images with relatively low resolution, so it is rather difficult to obtain detailed anatomical information from SPECT images.
The PET apparatus forms images of parts of the entire human body using the fact that a malignant tumor in the entire human body consumes more glucose than normal tissues. The PET apparatus makes it possible to provide early diagnosis of abnormal symptoms or diseases by visualizing degrees of sugar, oxygen, and protein metabolism in the entire human body. However, the PET apparatus cannot provide detailed information on, for example, where a tumor is located in the entire human body and how big the tumor is.
The above-described imaging apparatuses have different advantages and disadvantages. Therefore, for more accurate and more effective diagnosis and treatment of diseases, it would be desirable to get an image of a desired part of the entire human body using as many imaging apparatuses as possible and analyze the resultant images taken by the different imaging apparatuses by comparing them with one another.
For a more accurate comparative analysis of images taken by different imaging apparatuses, image registration, which is a technique of mapping the images on the same coordinate system, is necessary. The image registration operation indicates processes of mapping and overlapping various images of a desired part of the entire human body, taken by the different imaging apparatuses, on a given coordinate system, thus guaranteeing more accurate and more effective diagnosis and treatment of diseases.
An image registration tool, namely, image registration software, matches images of a desired portion of the entire human body, taken by different imaging apparatuses, with one another. Therefore, unless accuracy of the image registration software is guaranteed, reliability of image registration results cannot be attained. Inaccurate image registration results inevitably lead to inaccurate diagnosis and inappropriate treatment of diseases.
Therefore, research has been carried out on image registration, and development of image registration software that can provide very accurate image registration results in a more convenient manner is under way.
In the meantime, a phantom is necessary for evaluating the general performance and accuracy of the image registration software. The phantom makes it possible to obtain multiple images and more accurately carry out error analysis. In short, the phantom can be tomographed using various imaging apparatuses and are used for evaluating the accuracy of the image registration software and other necessary procedures.
Until now, no phantoms have been developed exclusively for evaluating the accuracy of image registration software. In other words, conventional phantoms have been mainly used to control the quality of imaging apparatuses or radioactive therapy equipment so that they can compare images at best two-dimensionally.